I have been having suspisions that it could be an issue with flouride I found an interesting article about aluminum flouride. Apparently under acidic conditions aluminum and flouride bond with a ph below 6I run mine at 5.6 and have flouride and aluminum in the water. Also everything I have been reading says that RO's don't remove flouride very well only an Alumina filter. I sent my water into the lab to have it tested I should know by today or tomorow whats in it. I added a few filters to my line up I have a KDF(zinc copper) and a tall blue. Going to get the Alumina if my tests come back with flouride in it.